The Landscape Change of Salt and Alkaline Land in Semi-Arid District before and after Flooding: A Case Study in Zhenlai County
洪水前后半干旱区盐碱地景观变化分析——以镇赉县为例

This paper adopted relief map and TM, SAR image, impaling the image disposal technology of Remote Sensing and the space analysis technology of Geography Information System, and combining landscape ecology theory to analyze the effect of flooding before and after 1998 on soil salinization. The analysis includes several aspects such as quantity, spatial distribution and landscape distribution of salt and alkaline land in Zhenlai County. The results show that the sum-acreage of saline-alkali land in Zhenlai County increased by 13 929.5hm2 after the flood. The connectivity and integrity of saline-alkali land increased as well. Furthermore, the center of Gravity of saline-alkali offset from west to east 1.57km. The offset of the flooded area is 1.53km, and that of the non-flooded area is 3.68km. The offset distance of the saline-alkali land in the non- flooded area is much bigger than that of the flooded area. Therefore, flooding has the effect to slow up the offset of the saline-alkali land while having the effect to push forward the offset of the saline-alkali land. By contrasting the change ratio of unit area of saline-alkali land between flooding zone and no-flooding zone, it is found that the change ratio of all kind of saline-alkali land in flooding zone is higher than that in no-flooding zone at large. For example, the ratio of heavy grade of saline-alkali land in flooding zone is 5 times of that in no-flooding zone. The ratio of moderate grade saline-alkali land in flooding zone is 4.5 times of that in no-flooding zone. The ratio of gentleness grade saline-alkali land in flooding zone is 1.1 times of that in no-flooding zone. It is concluded that the flooding has the effect to promote the extension of saline-alkali land in half arid district after the flooding. Though studying the integrity and average area of the saline-alkali patch of the landscape distribution, the landscape distribution of the saline-alkali land in the flooded area is obviously different from the non-flooded area. At the same time, the degree of salinization is higher in the flooded area than that in the non-flooded area after the flooding. The flooding push forward the speed and speed of the salinization in the half arid district where the terrain is low-lying and level of groundwater is higher.